(1) Field of the Invention
The present invention relates to an improvement of a solid cemented carbide ball nose end mill.
(2) Description of the Related Art
A conventional solid cemented carbide ball nose end mill comprises a substantially semi-spherical ball nose portion having cutting edges on the top end thereof and a tool body having a peripheral cylindrical portion with peripheral cutting edges extending from each of the cutting edges and a cylindrical or conical shank at the rear end thereof, as disclosed in U.S. Pat. No. 5, 558,475. Around the top end, two or four cutting edges each having a positive rake angle are symmetrically positioned as viewed from the top end, and the cutting edges extend over the peripheral cylindrical portion to form peripheral cutting edges having 0.5 to 3 times the length of the outer diameter of the end mill. In most cases, each surface of the cutting edges is coated with a hard material including a TiCN film. Such a solid cemented carbide ball nose end mill is frequently used for a three-dimensional machining of a metal mold which requires a higher speed and higher load cutting.
However, a metal mold and the like is generally made of a difficult-to-machine material like a quenched or hardened material. Accordingly, in case of a high efficient finish machining under a higher speed and higher load cutting, some troubles such as a chipping of the cutting edges and a poor cutting accuracy occurred.